The invention relates to a device for controlling the current through an inductive consumer having switching devices which function inductively, in particular magnetic valves in the fuel metering system of an internal combustion engine, with which it is possible to control the current during an attracting and maintenance phase.
It is generally known to include the flow of electric current through inductive consumers, which act as switching elements, such as magnetic valves or relays, in an open-loop or closed-loop electric current control circuit. This is because during a so-called attracting phase high output must be delivered to the inductive consumer, for instance in order to be able to attain the most exact possible switching behavior over time. During a maintenance phase immediately following the attracting phase, the flow of current through the consumer can be dropped, because no further mechanical work must be performed; instead, the only energy required is that for keeping the magnetic valve, for instance, open. This energy is oriented to the restoring force of the element to be switched.
Two-point current governors are known in inductive consumers, wherein the flow of current through these consumers is switched on and off periodically in accordance with the various intensity of the electric current. The particular switching points are determined on the basis of the voltage drop over a current measuring resistor.
Consumer current governors of the analog type are also known, in which the flow of current is dropped to a maintenance value after the end of the attracting phase, and this analog value is then maintained by means of an electric current closed-loop control circuit.
The particular current threshold both for the maximum attracting current and for the maintenance current are detected in the prior art either via two separate threshold switches, or via one threshold switch having a reversible switching threshold. In both cases, the expense for circuitry is considerable, and it is one of the objects of the invention to create a device which is as simple as possible for controlling the current through an inductive consumer. The control of the consumer current in such a device corresponds in part to a closed-loop control procedure as well.